But United's inability to secure other marquee targets this summer, including Spanish trio Thiago, Cesc Fabregas and Ander Herrera - over whom the club enquired about on deadline day - has led to senior club figures preparing an informal investigation into what went wrong.

It is thought that the club will look to use the international break to analyse their summer dealings, ahead of the players returning to training before hosting Crystal Palace on September 14.

Moyes, who remained at the club's Carrington training base late into Monday night to ensure the signing of Fellaini was completed before the 23.00BST deadline, has earmarked a number of potential incomings in recent months but saw all but the Belgian fall by the wayside.

Thiago, who joined former boss Pep Guardiola at Bayern Munich, had been the subject of talks between United and Barcelona in July, with the Red Devils keen to add a central midfielder to their ranks following Paul Scholes's retirement and the ongoing illness of Darren Fletcher.

Moyes also publicly declared an interest in signing Fabregas from Camp Nou but saw the former Arsenal star commit his future to the Catalan giants, with United having had two bids for the midfielder rejected.

The Premier League champions also saw a deadline day offer for Leighton Baines rebuffed by Everton chairman Bill Kenwright, who maintained the full-back was not for sale throughout the summer.

As such, United brought in only two players over the summer, with 20-year-old Uruguayan Guillermo Varela the only other arrival alongside Fellaini at Old Trafford.